How Much Sleep Do You Really Need?

Dunlop’s tipping point came when she got a new job that required her to show up at the office by 9 a.m. rather than the 10 a.m. start time she was used to at her previous job. “It was unrealistic to go to bed earlier than I already was, so I started getting seven-and-a-half hours of sleep at night.”

Surprisingly, Dunlop felt more alert, with enough extra energy to work out in the evenings. “I used to oversleep almost every day,” she says. “I'm not saying I suddenly jump out of bed all cheery now, but it's not as hard anymore.”

MORE: The Beauty Benefits of Sleep

Dunlop did her energy, and her health, a favor by scaling down her sleep schedule. New sleep research shows there is a U-shaped relationship between slumber and longevity, meaning that getting too little—or too much—sleep will raise your mortality rate. Numerous studies have come to the same conclusion: People who self-reported sleeping more than seven-and-a-half hours a night or less than six to six-and-a-half hours a night had an increased risk of death.

While not logging enough snooze time has a clear and direct affect on your health, “getting too much sleep—a condition called hypersomnia—isn’t a problem on its own per se,” says Dr. Shives. It’s the fact that oversleeping can be a red flag for an underlying health condition, such as obstructive sleep apnea—a dangerous disorder that causes people to stop breathing momentarily during sleep—and depression.

The optimal amount of sleep
So how much do you need to nab for a longer life? For years people have been told that when it comes to sleep, eight is the magic number, but that’s actually the upper range. Although most sleep experts recommend getting seven to eight hours of sleep on average, several studies show that getting around seven to seven-and-a-half hours a night lowers your mortality risk.

But don’t fret if you get more or less—it’s just an average, and you’re not going to die from not getting enough z’s one night. Also, keep in mind that many sleep studies are self-reported, meaning the study participants estimate how much shut-eye they believe they logged. But people aren’t always so good at ball-parking the amount of sleep they actually got.